New implantation method may produce more natural motion in patients with prosthetics

Erik G. Sorto, a quadriplegic patient, is able to control a robotic arm thanks to a neuroprosthesis that reads his intentions.

Researchers from California Institute of Technology have found a part of the brain that controls intuitive movement planning may play a key role in improving motor control among paralyzed patients though the use of a prosthesis.

According to a press release, the researchers have developed a way to produce more natural and fluid motions by implanting a neuroprosthesis in a part of the brain that controls the intent to move. The Caltech team and colleagues from Keck Medicine of University of Southern California successfully implanted such a device during a clinical trial in a patient with quadriplegia, giving him the ability to perform a fluid hand-shaking gesture and play “rock, paper, scissors” using a separate robotic arm, the release stated.

The results of the trial, which was led by principal investigator Richard Andersen, PhD, the James G. Boswell Professor of Neuroscience, were recently published in Science.

Erik G. Sorto, a quadriplegic patient, is able to control a robotic arm thanks to a neuroprosthesis that reads his intentions.

Source: Spencer Kellis and Christian Klaes/Caltech

“When you move your arm, you really do not think about which muscles to activate and the details of the movement — such as lift the arm, extend the arm, grasp the cup, close the hand around the cup and so on. Instead, you think about the goal of the movement. For example, ‘I want to pick up that cup of water,’” Andersen said in press release. “In this trial, we were successfully able to decode these actual intents by asking the subject to simply imagine the movement as a whole, rather than breaking it down into a myriad components.”

Previous neuroprosthetic designs have focused on detecting and recording signals at the motor cortex, which is the last stop for signals from the brain before they reach the spinal cord.

Andersen and colleagues aimed to improve the versatility of movement offered by a neuroprosthesis by recording signals from a different brain region: the posterior parietal cortex (PPC).

“The PPC is earlier in the pathway, so signals there are more related to movement planning — what you actually intend to do — rather than the details of the movement execution,” Andersen said in the release. “We hoped that the signals from the PPC would be easier for the patients to use, ultimately making the movement process more intuitive.”

During the clinical trial to test the safety and effectiveness of the new approach, surgeons implanted a pair of small electrode arrays in two parts of the PPC of a quadriplegic patient. Each array contained 96 active electrodes to record the activity of a single neuron in the PPC. The arrays were connected by a cable to a system of computers that processed the signals, decoded the intent of the subject and controlled output devices, including a computer cursor and a robotic arm, according to the release.

After recovering from the surgery, the patient was trained to control the computer cursor and the robotic arm with his mind. Upon completion of training, the patient successfully achieved intuitive movement of the robotic arm.

“For me, the most exciting moment of the trial was when the participant first moved the robotic limb with his thoughts. He had been paralyzed for over 10 years,” Andersen said in the release. “It was a big surprise that the patient was able to control the limb on day 1 — the very first day he tried.”

Reference:

Andersen R. Science. 2015; doi: 1010.1126/science.aaa5417.

Disclosure:

See the full study for a list of all authors’ relevant financial disclosures.